The invention relates to pipe couplings in general, and more particularly to improvements in couplings which can be used to separably connect to each other pipes with plain ends. Still more particularly, the invention relates to improvements in pipe couplings of the type wherein an arcuate housing is provided with one or more axially parallel slots and can be placed around the ends of the pipes which are to be coupled to each other preparatory to a reduction of the width of the slot or slots to thus urge annuli of teeth in the interior of the housing against and into the material of the ends of the pipes.
Couplings of the above outlined character are disclosed in commonly owned German Auslegeschrift No. 25 55 179 of Zeidler, in commonly owned copending patent application Ser. No. 079,659 filed July 29, 1987 by Zeidler for "Pipe coupling", and in commonly owned copending patent application Ser. No. 173,250 filed Mar. 24, 1988 by Zeidler et al. for "Pipe coupling". Similar pipe couplings are disclosed in commonly owned U.S. Pat. No. 4,729,582 granted Mar. 8, 1988 to Zeidler for "Pipe coupling".
Commonly owned U.S. Pat. Nos. 4,616,858 (granted Oct. 14, 1986 to Sauer for "Flexible pipe coupling"), 4,627,645 (granted Dec. 9, 1986 to Sauer for "Flexible pipe coupling) and 4,726,611 (granted Feb. 23, 1988 to Sauer for "Flexible pipe coupling) disclose toothless pipe couplings wherein the housing can urge the lips of an elastic sleeve-like insert against the ends of the pipes which are to be sealingly coupled to each other.
The teeth of pipe couplings which are disclosed in the Auslegeschrift and in copending patent applications of Zeidler and Zeidler et al. have flanks of identical size, and the flanks of each tooth make an angle which does not exceed 90 degrees. Such teeth (each of which consists of two mirror symmetrical halves) are considered desirable and advantageous because they are expected to readily penetrate into the material of the pipe ends to thereby hold the pipes against axial and/or other movement relative to each other. It has been found that pipe couplings which are provided with such teeth are not entirely satisfactory because the teeth which are adjacent the slot or slots of the housing are likely to shift the material of the respective pipe ends in the circumferential direction of the pipes when the width of the slot or slots is being reduced whereby the accumulations of the material of pipes at those flanks of teeth which are nearer to the adjacent slot or slots offer a pronounced resistance to further reduction of the width of the slot or slots so that the teeth which are remote from the slot or slots fail to penetrate into the material of the pipe ends or the tips of such remote teeth penetrate only negligibly so that their retaining action is unsatisfactory. The reason for such drawbacks of known pipe couplings is that the teeth which are nearest to the slot or slots of the housing are caused to move radially inwardly into the respective pipe ends as well as circumferentially of the pipes whereby their tips push the material of the pipes toward the adjacent slot or slots.